Zero-discharge recycling device for high-salinity wastewater

Abstract

The utility model belongs to the technical field of high-salinity wastewater recycling, and particularly relates to a high-salinity wastewater zero-discharge recycling device which comprises a wastewater pretreatment unit, an RO (Reverse Osmosis) pre-concentration unit and a low-pressure nanofiltration salt separation unit which are connected in sequence, and is characterized in that a concentrated water end of the low-pressure nanofiltration salt separation unit is connected with an inlet end of a sodium sulfate salt water blending tank through a pipeline; the outlet end of the sodium sulfate brine blending tank is connected with the inlet end of the double decomposition reaction device through a pipeline, the water production end of the low-pressure nanofiltration salt separation unit is connected with the inlet end of the ultra-multiple RO concentration unit, and the concentrated water end of the ultra-multiple RO concentration unit is connected with the inlet end of the saturated sodium chloride brine blending tank; and the outlet end of the saturated sodium chloride brine blending tank is connected with the ionic membrane electrolytic cell. The system is high in resource utilization rate, does not generate any secondary pollution such as industrial waste salt, hazardous waste mother liquor carnallite and the like, and realizes all cyclic utilization of water and materials.

Description

Technical Field

[0001] The utility model belongs to the technical field of high-salt wastewater resource utilization, and specifically relates to a zero-discharge resource utilization device for high-salt wastewater. Background Art

[0002] High-salt wastewater refers to wastewater with a total salt mass fraction of at least 1%. It mainly comes from chemical plants and the collection and processing of oil and natural gas, etc. This kind of wastewater contains various substances (including salts, oils, organic heavy metals, and radioactive substances), and it is crucial to remove the impact on the environment caused by organic pollutants in saline wastewater. The existing zero-discharge devices for high-salt wastewater include a wastewater pretreatment unit, an RO pre-concentration unit, a low-pressure nanofiltration salt separation unit, and a branch of the low-pressure nanofiltration salt separation unit are sequentially connected to a high-pressure nanofiltration unit and a freezing crystallizer for producing sodium sulfate, and another branch of the low-pressure nanofiltration salt separation unit is sequentially connected to a reverse osmosis unit for nanofiltration-produced water, an electrodialysis unit, and an MVR evaporation crystallizer for producing sodium chloride.

[0003] The zero-discharge device for high-salt wastewater with the above structure has many drawbacks and is difficult to truly achieve the goal of reducing pollution, reducing emissions, and recycling:

[0004] 1) It requires processes such as pretreatment, multi-stage membrane concentration, nanofiltration salt separation, freezing crystallization, ED concentration, and evaporation. The process is long, the investment is huge, and the operating cost is too high;

[0005] 2) The operating reliability of the evaporation system and the freezing crystallization system is poor, and the management is complicated;

[0006] 3) A large amount of industrial waste salt and a small amount of hazardous waste mother liquor are difficult to utilize, actually forming hazardous solid waste, resulting in uncontrollable actual operating costs of the system. If the system operates continuously for a long time, enterprises cannot bear the high environmental protection costs.

[0007] In order to solve the above problems, the inventor Cao Cheng of this application applied for a utility model patent named a zero-discharge device for high-salt wastewater to the Chinese Patent Office on January 16, 2023. This patent was authorized and announced on May 26, 2023, and the authorization announcement number is CN219079306U. It abandons the nanofiltration salt separation and subsequent RO re-concentration, ED concentration, evaporation, and freezing crystallization process sections in the existing zero-discharge device for high-salt wastewater, greatly reducing the investment and operating costs of environmental protection facilities. At the same time, it realizes the reduction of pollutants and resource utilization of high-salt wastewater by chemical technology means, uses RO concentrated brine or the produced water and concentrated water after nanofiltration salt separation as one of the raw materials for chemical production respectively to produce industrial-grade baking soda, ammonium chloride, ammonium sulfate, or potassium sulfate, turning negative benefits into positive benefits, while taking into account ecological environmental protection and economic benefits, and promoting the environmental protection project to truly achieve the coordinated efficiency of pollution control, emission reduction, and carbon reduction and long-term sustainable operation.

[0008] In actual promotion and use, the applicant found that the above-mentioned patented technology still has the following defects:

[0009] The degree of resource utilization is not high enough. Utility Model Content

[0010] The purpose of the present utility model is to provide a zero-discharge resource utilization device for high-salt wastewater, whose resource utilization products are more abundant, and can produce sodium hydroxide, chlorine, hydrogen, sodium bicarbonate, ammonium chloride, ammonium sulfate or potassium sulfate, thereby improving economic benefits.

[0011] The present utility model is realized through the following technical solutions:

[0012] That is, a zero-discharge resource utilization device for high-salt wastewater, including a wastewater pretreatment unit, an RO pre-concentration unit, and a low-pressure nanofiltration salt separation unit connected in sequence. It is characterized in that the concentrated water end of the low-pressure nanofiltration salt separation unit is connected to the inlet end of the sodium sulfate brine preparation tank through a pipeline, the outlet end of the sodium sulfate brine preparation tank is connected to the inlet end of the double decomposition reaction device through a pipeline, the water production end of the low-pressure nanofiltration salt separation unit is connected to the inlet end of the ultra-multiple RO concentration unit, the concentrated water end of the ultra-multiple RO concentration unit is connected to the inlet end of the saturated sodium chloride brine preparation tank, and the outlet end of the saturated sodium chloride brine preparation tank is connected to an ion membrane electrolytic cell.

[0013] The reaction kettle and the crystallizer of the double decomposition reaction device of the present utility model are both mature commercially available products in the prior art, and those skilled in the art know their structures and usage methods.

[0014] The high-salt wastewater is pretreated by the wastewater pretreatment unit to remove hardness, impurities and reduce COD, and then concentrated by the RO pre-concentration unit. The produced pure water is recycled, and the concentrated brine is separated by nanofiltration into two production sections. Section 1: The nanofiltration produced water is sodium chloride concentrated brine as a production raw material, sodium chloride is added to prepare saturated brine, and sodium hydroxide, chlorine and hydrogen are produced through the ion membrane electrolysis process. Section 2: The nanofiltration concentrated water is sodium sulfate concentrated brine as a production raw material, ammonium bicarbonate is added, and sodium bicarbonate and ammonium sulfate are produced through the reaction kettle, and the evaporation condensate water is recycled.

[0015] Further, the outlet end of the reaction kettle of the double decomposition reactor of the present utility model is connected to the inlet end of the saturated sodium chloride brine preparation tank through a pipeline.

[0016] In the above solution, the high-salt wastewater is pretreated by the wastewater pretreatment unit to remove hardness, impurities and reduce COD, and then concentrated by the RO pre-concentration unit. The produced pure water is recycled, and the concentrated brine is separated by nanofiltration into two production sections. Section 1: The nanofiltration produced water is concentrated sodium chloride brine as the production raw material, sodium chloride is added to prepare saturated brine, and sodium hydroxide, chlorine and hydrogen are produced through the ion-exchange membrane electrolysis process. Section 2: The nanofiltration concentrated water is concentrated sodium sulfate brine as the production raw material, potassium chloride is added, and potassium sulfate is produced through the reaction kettle. At the same time, the produced saturated sodium chloride solution is used as the raw material for production section 1.

[0017] The utility model has the following advantages:

[0018] 1) The utility model produces many products and has a high level of resource utilization;

[0019] 2) The utility model does not produce any secondary pollution such as industrial waste salt and hazardous waste mother liquor miscellaneous salt, realizes the full recycling of water and materials, and completely solves the pain points existing in the existing zero-discharge device for high-salt wastewater. Description of the Drawings

[0020] Figure 1 is a schematic structural diagram of Embodiment 1 of the utility model;

[0021] Figure 2 is a schematic structural diagram of Embodiment 2 of the utility model;

[0022] As shown in the figure: 1. Wastewater pretreatment unit; 2. RO pre-concentration unit; 3. Low-pressure nanofiltration salt separation unit; 4. Sodium sulfate brine preparation tank; 5. Double decomposition reaction device; 6. Ultra-multiplication RO concentration unit; 7. Saturated sodium chloride brine preparation tank; 8. Ion-exchange membrane electrolytic cell. Specific Embodiments

[0023] The embodiments of the technical solution of the utility model will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of the utility model more clearly, so they are only examples and cannot be used to limit the protection scope of the utility model. It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which the utility model belongs. Embodiment 1

[0024] As Figure 1As shown in the figure: The wastewater pretreatment unit 1, RO preconcentration unit 2, and low-pressure nanofiltration salt separation unit 3-2 are connected in sequence by pipelines. The water production end of the low-pressure nanofiltration salt separation unit 3-2 is connected to the inlet end of the sodium sulfate brine preparation tank 4 through a pipeline. The outlet end of the sodium sulfate brine preparation tank 4 is connected to the inlet end of the double decomposition reaction device 5 through a pipeline. The concentrated water end of the low-pressure nanofiltration salt separation unit 3-2 is connected to the inlet end of the super RO concentration unit 6 through a pipeline. The concentrated water end of the super RO concentration unit 6 is connected to the inlet end of the saturated sodium chloride brine preparation tank 7 through a pipeline. The outlet end of the sodium chloride brine preparation tank 7 is connected to the ion membrane electrolyzer 8 through a pipeline.

[0025] In the use of this embodiment, the high-salt wastewater enters the RO preconcentration unit 2 after being dehardened, desalted, and COD-reduced by the wastewater pretreatment unit 1. The produced water is recycled, and the concentrated water passes through the low-pressure nanofiltration membrane salt separation unit 3-2. The produced water is sodium chloride concentrated solution, and the concentrated water is sodium sulfate concentrated solution. Subsequently, it is divided into two production sections. Section 1: The nanofiltration produced water is sodium chloride concentrated brine, which is further concentrated by the super RO concentration unit 6. The produced water is recycled, and the concentrated water enters the saturated sodium chloride brine preparation tank 7 and sodium chloride is added for preparation to form saturated sodium chloride brine as a production raw material, and sodium hydroxide, chlorine, and hydrogen are produced through the ion membrane electrolyzer 8. Section 2: The nanofiltration concentrated water is sodium sulfate concentrated brine, which is used as a production raw material. After being prepared in the sodium sulfate brine preparation tank 4, ammonium bicarbonate is added, and baking soda (sodium bicarbonate) precipitate crystals are generated through the reaction kettle of the double decomposition reaction device 5. The filtrate is evaporated, salted out, cooled to precipitate ammonium sulfate, and the evaporation condensate water is recycled. Example 2

[0026] As Figure 2 shown in the figure: The outlet end of the reaction kettle of the double decomposition reactor 5 is connected to the inlet end of the saturated sodium chloride brine preparation tank 7 through a pipeline, and the others are the same as Example 2.

[0027] In the use of this embodiment, Section 2: The nanofiltration concentrated water is sodium sulfate concentrated brine, which is used as a production raw material. After being prepared in the sodium sulfate brine preparation tank 4, potassium chloride is added. Through the double decomposition reaction device 5, the filtrate is evaporated, salted out, cooled to precipitate potassium sulfate, and the evaporation condensate water is recycled. The by-product saturated sodium chloride solution enters the saturated sodium chloride brine preparation tank 7 as a raw material for Section 1 of the production process, and the others are the same as Example 1.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. A zero-emission and resource-recovery device for high-salt wastewater, comprising a wastewater pretreatment unit, an RO pre-concentration unit, and a low-pressure nanofiltration salt-splitting unit that are connected in sequence, characterized in that The concentrated water end of the low-pressure nanofiltration salt separation unit is connected to the inlet end of the sodium sulfate brine preparation tank through a pipeline. The outlet end of the sodium sulfate brine preparation tank is connected to the inlet end of the metathesis reaction device through a pipeline. The water production end of the low-pressure nanofiltration salt separation unit is connected to the inlet end of the super RO concentration unit. The concentrated water end of the super RO concentration unit is connected to the inlet end of the saturated sodium chloride brine preparation tank. The outlet end of the saturated sodium chloride brine preparation tank is connected to the ion-exchange membrane electrolytic cell.

2. The zero-emission resource utilization device for high-salt wastewater according to claim 1, characterized in that The outlet end of the reaction kettle of the metathesis reactor is connected to the inlet end of the saturated sodium chloride brine preparation tank through a pipeline.

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